• Membrane and Water Treatment
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• 제11권1호
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• pp.69-77
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• 2020

Former studies revealed that sepiolite thermally treated at high temperature have high adsorption capacity for phosphate. However, its micron size (75 ㎛) limits its application to water treatment. In this study, we synthesized sepiolite impregnated polysulfone (PSf) beads to separate it easily from an aqueous solution. PSf beads with different sepiolite ratios were synthesized and their efficiencies were compared. The PSf beads with 30% impregnated sepiolite (30SPL-PSf bead) possessed the optimum sepiolite ratio for phosphate removal. Kinetic, equilibrium, and thermodynamic adsorption experiments were performed using the 30SPL-PSf bead. Equilibrium adsorption was achieved in 24 h, and the pseudo-first-order model was suitable for describing the phosphate adsorption at different reaction times. The Langmuir model was appropriate for describing the phosphate adsorption onto the 30SPL-PSf bead, and the maximum adsorption capacity of the 30SPL-PSf bead obtained from the model was 24.48 mg-PO₄/g. Enthalpy and entropy increased during the phosphate adsorption onto the 30SPL-PSf bead, and Gibb's free energy at 35 ℃ was negative. An increase in the solution pH from 3 to 11 induced a decrease in the phosphate adsorption amount from 27.30 mg-PO₄/g to 21.54 mg-PO₄/g. The competitive anion influenced the phosphate adsorption onto the 30SPL-PSf bead was in the order of NO₃^- > SO₄^2- > HCO_3^-. The phosphate breakthrough from the column packed with the 30SPL-PSf bead began after ~2000 min, reaching the influent concentration after ~8000 min. The adsorption amounts per unit mass of 30SPL-PSf and removal efficiency were 0.775 mg-PO₄/g and 61.6%, respectively. This study demonstrates the adequate performance of 30SPL-PSf beads as a filter for phosphate removal from aqueous solutions.

• 한국환경과학회지
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• 제19권5호
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• pp.549-563
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• 2010

The environmental behaviors of polycyclic aromatic hydrocarbons (PAHs) are mainly governed by their solubility and partitioning properties on soil media in a subsurface system. In surfactant-enhanced remediation (SER) systems, surfactant plays a critical role in remediation. In this study, sorptive behaviors and partitioning of naphthalene in soils in the presence of surfactants were investigated. Silica and kaolin with low organic carbon contents and a natural soil with relatively higher organic carbon content were used as model sorbents. A nonionic surfactant, Triton X-100, was used to enhance dissolution of naphthalene. Sorption kinetics of naphthalene onto silica, kaolin and natural soil were investigated and analyzed using several kinetic models. The two compartment first-order kinetic model (TCFOKM) was fitted better than the other models. From the results of TCFOKM, the fast sorption coefficient of naphthalene ($k_1$) was in the order of silica > kaolin > natural soil, whereas the slow sorbing fraction ($k_2$) was in the reverse order. Sorption isotherms of naphthalene were linear with organic carbon content ($f_{oc}$) in soils, while those of Triton X-100 were nonlinear and correlated with CEC and BET surface area. Sorption of Triton X-100 was higher than that of naphthalene in all soils. The effectiveness of a SER system depends on the distribution coefficient ($K_D$) of naphthalene between mobile and immobile phases. In surfactant-sorbed soils, naphthalene was adsorbed onto the soil surface and also partitioned onto the sorbed surfactant. The partition coefficient ($K_D$) of naphthalene increased with surfactant concentration. However, the $K_D$ decreased as the surfactant concentration increased above CMC in all soils. This indicates that naphthalene was partitioned competitively onto both sorbed surfactants (immobile phase) and micelles (mobile phase). For the mineral soils such as silica and kaolin, naphthalene removal by mobile phase would be better than that by immobile phase because the distribution of naphthalene onto the micelles ($K_{mic}$) increased with the nonionic surfactant concentration (Triton X-100). For the natural soil with relatively higher organic carbon content, however, the naphthalene removal by immobile phase would be better than that by mobile phase, because a high amount of Triton X-100 could be sorbed onto the natural soil and the sorbed surfactant also could sorb the relatively higher amount of naphthalene.

• 청정기술
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• 제26권1호
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• pp.30-38
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• 2020

입상 활성탄에 대한 Acid Red 66의 흡착 등온선과 동력학적, 열역학적 파라미터에 대해 염료의 초기농도, 접촉시간, 온도를 흡착변수로 하여 조사하였다. 흡착평형자료는 Langmuir, Freundlich, Temkin, Redlich-Peterson 및 Temkin 등온흡착식에 적용하였다. Freundlich 등온흡착식이 가장 잘 맞았으며, 계산된 Freundlich 분리계수 값(1/n = 0.125 ~ 0.232)으로부터 입상 활성탄이 Acid Red 66을 효과적으로 처리할 수 있다는 것을 알 수 있었다. Temkin의 흡착열관련상수(B_T = 2.147 ~ 2.562 J mol^-1)는 이 공정이 물리흡착임을 나타냈다. 동력학적 실험으로부터 흡착공정은 유사 이차 반응속도식에 잘 맞았다. 입자 내 확산식에 대한 결과는 경계층 확산을 나타내는 첫 번째 직선의 기울기보다 입자내 확산을 나타내는 두 번째 직선의 기울기가 작게 나타나서 입자 내 확산이 율속단계인 것을 확인하였다. 열역학 실험으로부터 활성화 에너지는 35.23 kJ mol^-1로 흡착공정이 물리흡착공임을 확인하였다. Gibbs 자유에너지 변화(ΔG = -0.548 ~ -7.802 kJ mol^-1)와 엔탈피 변화(ΔH = +109.112 kJ mol^-1)은 각각 흡착공정이 자발적 공정 및 흡열과정임을 나타내었다. 등량흡착열은 흡착된 염료분자들의 측면상호작용을 나타내는 표면부하량이 증가함에 따라 증가하였다.

• 청정기술
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• 제26권2호
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• pp.122-130
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• 2020

입상 활성탄에 대한 reactive blue 4 (RB 4) 의 등온흡착과 동력학적, 열역학적 파라미터에 대해 활성탄의 양, pH, 초기농도, 접촉시간, 온도를 흡착변수로 하여 조사하였다. 활성탄에 의한 RB 4 염료의 흡착은 pH 7을 기점으로 양쪽으로 흡착 백분율이 증가하는 concave 모양을 나타내었다. 등온흡착자료는 Langmuir, Freundlich, Temkin 등온흡착식에 적용하였다. Freundlich과 Langmuir 등온흡착식이 모두 잘 맞았다. 계산된 Freundlich 분리계수(1/n = 0.125 ~ 0.232)과 Langmuir 분리계수(R_L = 1.53 ~ 1.59) 으로부터 활성탄이 RB 4를 효과적으로 처리할 수 있다는 것을 알 수 있었다. Temkin의 흡착열관련상수(B_T = 17.611 ~ 29.010 J mol^-1)는 이 공정이 물리흡착임을 나타냈다. 동력학적 실험으로부터 흡착공정은 유사 이차 반응속도식에 잘 맞았다. 입자 내 확산식에 대한 결과는 표면확산을 나타내는 두 번째 직선의 기울기보다 입자내 세공확산을 나타내는 첫 번째 직선의 기울기가 작게 나타나서 입자내 세공확산이 속도지배단계인 것을 확인하였다. Gibbs 자유에너지 변화(ΔG = -3.262 ~ -7.581 kJ mol^-1)와 엔탈피 변화(ΔH = 61.08 kJ mol^-1)은 각각 흡착공정이 자발적 공정 및 흡열과정임을 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2377-2381
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• 2007

Solvolyses of 3,4-dimethoxybenzenesulfonyl chloride (DSC) in water, D2O, CH3OD, and in aqueous binary mixtures of acetone, acetonitrile, 1,4-dioxane, ethanol, methanol, and 2,2,2-trifluoroethanol (TFE) have been investigated at 25.0 oC. Kinetic solvent isotope effects (KSIE) in water and in methanol and product selectivities in alcohol-water mixtures are also reported. The Grunwald-Winstein plot of first-order rate constants for the solvolyic reaction of DSC with YCl shows marked dispersions into separated lines for various aqueous mixtures. With use of the extended Grunwald-Winstein equation, the l and m values obtained are 1.12 and 0.58 respectively for the solvolyses of DSC. The relatively large magnitude of l is consistent with substantial nucleophilic solvent assistance. From Grunwald-Winstein plots the rate data are dissected approximately into contributions from two competing reaction channels. This interpretation is supported for alcohol-water mixtures by the trends of product selectivities, which show a maximum for ethanol-water mixtures. From the KSIE of 1.45 in methanol, it is proposed that the reaction channel favored in methanolwater mixtures and in all less polar media is general-base catalysed and/or is possibly (but less likely) an addition-elimination pathway. Also, the KISE value of 1.35 for DSC in water is expected for SN2-SN1 processes, with minimal general base catalysis, and this mechanism is proposed for solvolyses in the most polar media.

• 한국추진공학회지
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• 제22권1호
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• pp.66-71
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• 2018

에너지 물질의 수명평가는 중요하게 여겨지지만, 여러 가지 어려움을 갖고 있다. 먼저 노화시험에 매우 긴 시간이 소요되고, 에너지 물질이기 때문에 취급 시 항상 위험이 존재한다. 이런 이유들로 인해서 예측이나 계산 방법들이 발달되어 왔다. 에너지 물질은 열을 내놓으면서 분해되기 때문에, 에너지 물질의 열적 특성을 분석하는 것은 에너지 물질의 분해와 노화 특성을 이해하는데 매우 중요하다. 이번 연구에서는 첫째, DSC를 기초데이터로 하여 AKTS software를 이용하여 간단한 열분석으로부터 열적인 노화 특성을 예측하는 결과들을 발표하고, 둘째, AKTS software를 통해 물성측정 점 데이터로부터 적절한 kinetic 모델을 설정하고, 그 모델로부터 노화에 따른 특성변화를 예측하는 결과를 나타내었다.

• Journal of Radiation Protection and Research
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• 제27권2호
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• pp.121-126
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• 2002

본 연구는 지하수로부터 방출되어 가옥의 실내에 존재하는 라돈에 의한 체내축적량을 현실적으로 평가하는 방법을 보여준다. 먼저 지하수로부터 실내공기로 전달되는 과정을 모의하기 위해 2_구역모델을 개발하였다. 이 모델은 실내에서 발생하는 생활활동, 즉, 목욕, 세수, 세탁, 변기에서의 물사용에 의해 실내로 휘발, 이동하는 시간에 따를 라돈농도분포를 계산한다. 다음, 이 모델의 불확실성이 존재하는 입력인자들에 대해 불확실성분석을 수행하여 최종 실내라돈 농도분포를 결정하였다. 그리고 이러한 실내 라돈을 호흡하여 체내에 축적되는 양을 보다 정량적으로 모의하기 위해 PBPK 모델을 개발하였다. 불확실성이 포함된 라돈농도분포와 정량적인 체내축적모의를 위한 PBPK 모델의 결합으로 보다 현실적인 라돈의 체내축적량을 분석할 수 있다. 이러한 연구의 결과는 지하수로부터 발생하는 라돈에 의한 인체위해평가시 도움을 주리라고 판단된다.

• Journal of Applied Biological Chemistry
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• 제55권4호
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• pp.235-239
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• 2012

사과에 대한 diniconazole과 metconazole의 반감기와 잔류양상을 조사하였다. Diniconazole과 metconazole의 잔류허용기준은 둘 다 1.0 mg/kg으로서 0일차 기준량과 3회 처리구 모두 잔류 허용기준을 넘지 않았다. 재배기간 중 사과의 잔류농도는 약제살포 후 14일 경과 시 diniconazole은 기준량 및 3회 처리에서 0.01 및 0.02 mg/kg으로서 각각 88.9 및 93.8%의 농약이 분해되었다. Metconazole은 각각 0.04 및 0.11 mg/kg으로서 60.0 및 56.0% 정도의 농약 분해율을 보였다. Diniconazole의 사과중 반감기식은 기중량 처리구에서 y=$0.0811e^{-0.179x}$ ($r^2$=0.9693), 3회 처리구에서 y=$0.1451e^{-0.148x}$ ($r^2$=0.9677)이었으며 생물학적 반감기는 각각 3.9일 및 4.7일 이었다. Metconazole의 반감기식은 y=$0.0857e^{-0.055x}$ ($r^2$=0.9242) 및 y=$0.2304e^{-0.052x}$ ($r^2$=0.9544)이었고 생물학적인 반감기는 각각 12.6일 및 13.3일 이었다. Metconazole 기준량과 3회 처리의 경우 first order kinetic model 보다는 second order kinetic mode이 더 적합하였으며 반감기도 기준량에서 2일, 3회 처리에서 1일 감소되는 것을 알 수 있었다. 따라서 각 농약별로 잔류량과 시간과의 관계에 적합한 model을 찾아 반감기를 산출하는 것이 바람직 할 것으로 생각된다.

• 한국기계가공학회지
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• 제7권2호
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• pp.52-59
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• 2008

The objective of this study is to develop an automatic object changer unit to improve processing problems existed in the conventional horizontal machining center. To achieve this goal, this study designed a horizontal transfer as the second project continued to the first project that designed a upward and downward traverse unit. A horizontal traverse unit shows a symmetric structure and consists of frame, which consists of four unit tools, motor and reducer, which are fixed at a frame, operation unit with pinions, first traverse unit, and second traverse unit. Constraint conditions based on the operation mechanism with these elements were configured and obtained following results after modeling a model for a traverse motor. In the kinematic expression of sliding motion with one degree of freedom, the sliding motion is constrained. Also, the rack 3 installed at a frame is used to configure possible kinematic constraint conditions of the rack 2 according to the rolling motion of the pinion 2 in the first traverse unit. In addition, the moment of inertia that is a type of kinetic energy in a converted horizontal traverse unit in the side of the reducer can be applied to introduce the moment of inertia of a converted horizontal traverse unit in the side of the reducer by using the sum of kinetic energy in the rack and pinion, which is a part of the horizontal traverse unit. Also, the equation of motion of the converted upward and downward traverse unit in the side of the motor using the equation of motion of the motor. Furthermore, the horizontal traverse unit predetermines the mass of the first and second traverse unit and applied load including the radius and reduction ratio of the pitch circle in the pinion 1 and applied load to the rack 2. Then, a proper motor can be determined using several parameters in the upward and downward traverse unit in order to verify such predetermined specifications. In future studies later this study, a simulation that verifies the results of the previous two stages of studies using a finite element method.

• 한국토양비료학회지
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• 제51권1호
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• pp.8-15
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• 2018

A portion of the veterinary antibiotics administrated to livestock are generally excreted via feces and urine. Tetracyclines and tylosin have a greater priority of environmental risk in Korea based on the consumption and the potential to reach soil and water environment. The antibiotics in animal byproducts need to be reduced or eliminated before they are applied to agricultural lands through composting or other agricultural practices. The objective of the study was to investigate the effect of aeration on degradation of antibiotics during storage of swine slurry. Two antibiotics, tetracycline (TC) and tylosin (TYL), were detected from the swine slurry used in the study. One hour aeration per day for 62 days reduced TC concentration from 199 to $43ng\;L^{-1}$ compared with $104ng\;L^{-1}$ without aeration. Aeration for three and six hours decreased TC level to 30 and $23ng\;L^{-1}$, respectively. The dissipation of TC was fitted with a first-order kinetic model. Aeration for 1, 3, and 6 hours every day increased the first-order rate constant, k, from $0.011day^{-1}$ under anaerobic condition to 0.022, 0.026, and $0.037day^{-1}$, respectively. For TYL, aeration during storage of swine slurry enhanced k from $0.0074day^{-1}$ to 0.014, 0.018, and $0.031day^{-1}$ for 1, 3, and 6 hours per day, respectively. For liquid swine slurry, biotic processes can be more effective for dissipation of antibiotics than abiotic processes because of low organic matter and high water content. These results suggest that aeration can increase the degradation rate of antibiotics during storage of swine slurry.